WO2003006388A1

WO2003006388A1 - Method for starting up a system for treating waste by hydrothermal oxidation

Info

Publication number: WO2003006388A1
Application number: PCT/FR2002/002428
Authority: WO
Inventors: François CANSELL; Manuel Bottreau
Original assignee: Centre National De La Recherche Scientifique (C.N.R.S.)
Priority date: 2001-07-10
Filing date: 2002-07-10
Publication date: 2003-01-23
Also published as: KR20040040430A; US20060237352A1; KR100967571B1; US7326337B2; CN1543441A; JP4146337B2; CA2453181A1; CN1246236C; JP2004533930A; BR0211225A; US7063795B2; US20040238460A1; BR0211225B1; FR2827272A1; CA2453181C; MXPA04000194A; FR2827272B1; EP1404622A1

Abstract

The invention relates to a method for starting up a system for oxidating organic bodies. Said system comprises a tubular body (10) wherein an aqueous body is injected into the inlet (12) thereof at a pressure P1, said tubular body (10) having a first zone (16) extending the inlet (12) thereof, a second zone (18) into which an oxidating compound can be injected into the output (14) thereof. The inventive method comprises the following steps: a first amount of thermal energy Q1 is provided in the first zone (16), said amount of thermal energy being able to raise the temperature of the liquid flowing through said tubular body (10) from an initial temperature to a higher temperature T1; and a determined amount of a combustible mixture which can react at said intermediate temperature T1 in order to provide an amount of thermal energy Q2 bringing the temperature of said liquid to a reaction temperature T2 is injected.

Description

Method for starting a hydrothermal oxidation waste treatment installation

The present invention relates to a method for starting an installation intended for the oxidation of organic bodies contained in an aqueous effluent, as well as to a starting assembly intended for implementing said method.

A field of application envisaged is notably, but not exclusively, that of the start-up of installations making it possible to transform organic bodies contained in small quantities in aqueous effluents, into gases capable of being burned to provide energy or to be released. in the safe atmosphere.

Installations intended to oxidize the organic bodies contained in aqueous effluents are known, and one of the first stages of implementation of the processes generally consists in preheating the aqueous mixture containing said bodies so that their degradation can start as soon as one injects the oxidant. During normal operation of the installation, the thermal energy produced by the degradation of organic bodies is captured to preheat the aqueous mixture.

However, the normal operation of the installation is likely to be interrupted and its start-up again implemented, the preheating of the aqueous effluent can only be carried out by additional means, generally of the thermoelectric type, since there is no thermal energy available for degradation. Thus, the oxidation installation must include preheating means, thermoelectric or other, important and expensive whose duration of use is relatively short in comparison with the periods of treatment of the aqueous effluent which can reach several days and during which the oxidation reaction produces enough energy to preheat the aqueous effluent. A problem which arises and which the present invention aims to solve is then to reduce the power of the preheating means necessary for starting up the installation intended for the oxidation of organic bodies so as to reduce the cost of the installation without as well jeopardize said start-up.

To this end, a first object of the present invention is to propose a method for starting an installation, intended for the oxidation of organic bodies contained in an aqueous effluent, said installation comprising a tubular body at the inlet of which said aqueous effluent is capable of being injected at a pressure P1 corresponding at least to the critical pressure of said aqueous effluent, said tubular body having a first zone extending said inlet, a second zone into which an oxidizing composition is capable of being injected, and output ; process according to which: a first quantity of thermal energy Q1 is provided in said first zone of said tubular body, capable of bringing the temperature of the fluid which passes through said tubular body, from an initial temperature to an upper intermediate temperature T1; and, in said tubular body, at said pressure P1, is injected between said inlet and said first zone of said tubular body, a determined quantity of a combustible mixture capable of reacting at a temperature below the oxidation temperature of organic bodies and at least a first part of which is capable of reacting at said intermediate temperature T1 to supply a second quantity of thermal energy Q2, bringing the temperature of said fluid to a reaction temperature T2 so that the injection of said oxidizing composition into said second zone produces at least the reaction of a second part of said combustible mixture, supplying a third quantity of energy Q3 at said outlet from said tubular body, a fraction of said third quantity of energy Q3 being capable of being applied in said first area of said tubular body for carrying the temperature of the fluid passing through it, at least from said initial temperature to said intermediate temperature T1. Thus, a characteristic of the starting process resides in the mode of production of the preheating thermal energy necessary for the degradation of the organic bodies of the aqueous effluent, by means of a combustible mixture capable of reacting easily at a temperature T1 lower than the temperature T2 at which said organic bodies oxidize and which supplies the energy necessary to bring said first organic bodies to at least this temperature T1. In this way, it is no longer necessary to use significant additional preheating means to bring the temperature of the aqueous effluent to said temperature T2 but simply preheating means capable of producing a first quantity of energy Q1 carrying the temperature of the effluent at a temperature T1 lower than T2.

Advantageously, it ceases to supply said first quantity of energy Q1 in said first zone of said tubular body, when - said fraction of said third quantity of energy Q3 is at least equal to Q1. Thus, as soon as at least the reaction of said second part of said combustible mixture makes it possible to produce enough energy to supplement the additional preheating means, the latter are stopped. Preferably, the injection of said combustible mixture is stopped in order to inject said aqueous effluent at the inlet of said tubular body when said fraction of said third quantity of energy Q3 is at least equal to the sum of Q1 and Q2 so as to bring the temperature of the fluid passing through said tubular body from said initial temperature to said reaction temperature T2. As will be explained in more detail in the following description, when the thermal energy produced by the reaction of the combustible mixture has reached a certain threshold corresponding to the thermal equilibrium of the installation, only the aqueous effluent is injected to oxidize the organic bodies it contains. The thermal energy produced by the degradation of these organic bodies from the effluent alone makes it possible to preheat the aqueous effluent and bring it to the reaction temperature T2. According to a particularly advantageous embodiment of the invention, said combustible mixture comprises a fuel and an oxidant in sub-stoichiometric proportion so that a first portion of said fuel reacts with said oxidant when said combustible mixture is brought to said temperature T1 to supply said second quantity of energy Q2 and for the second portion of said fuel to react with said oxidizing composition. This characteristic makes it possible to reserve a second portion of fuel capable of reacting with the oxidizing composition and thus of producing said quantity of energy Q3, a fraction of which allows preheating.

In a particularly advantageous manner, said fuel and said oxidizer are capable of releasing an amount of energy greater than 3 ega Joules per mole of fuel molecules. In this way, small amounts of fuel are required to start the installation. And, preferably, said fuel has an activation energy of less than 1 Kilo Joules per mole of molecules of said fuel. Thus, the intermediate temperature T1 required to start the reaction is relatively low, so that a small amount of energy Q1 is required, which decreases the necessary power of the additional preheating means.

According to a particular embodiment of the invention, said oxidizer consists of hydrogen peroxide, which is relatively inexpensive and has a strong oxidizing power at the temperature and pressure conditions of the reaction. Preferably, said fuel comprises glucose, the cost of which is also advantageous and the implementation of which is easy.

Advantageously, said second quantity of energy Q2 that said combustible mixture is capable of providing represents, between 40 and 80% of the sum of Q1 and Q2, so that the reduction in size of the preheating means necessary for starting is substantial. According to a preferred embodiment, said combustible mixture is injected at the inlet of said tubular body in the same way as the aqueous effluent.

A second object of the present invention is to propose a start-up assembly implementing the method of the invention according to its first object. To do this, said starting assembly comprises: means for supplying, in said first zone of said tubular body, a first quantity of thermal energy Q1, capable of bringing the temperature of the fluid which passes through said tubular body, from an initial temperature at an upper intermediate temperature T1; and, means for injecting into said tubular body, at said pressure P1, between said inlet and said first zone of said tubular body, a determined quantity of a combustible mixture, of which at least a first part is capable of reacting at said intermediate temperature T1 to supply a second quantity of thermal energy Q2, bringing the temperature of said fluid to a reaction temperature T2 so that the injection of said oxidizing composition into said second zone produces at least the reaction of a second part of said combustible mixture , supplying a third quantity of energy Q3 to said outlet of said tubular body, a fraction of said third quantity of energy Q3 being capable of being applied in said first zone of said tubular body to bring the temperature of the fluid passing through it, to the less than said initial temperature at said intermediate temperature T1. Thus, according to its second object, the invention relates to an assembly for starting an installation comprising means for injecting a combustible mixture into the tubular body and means for supplying a first quantity of energy Q1, which is less than the amount of energy which it is necessary to supply with the installations of the prior art to preheat the fluid, since the reaction of the highly exothermic fuel mixture provides energy capable of compensating for the difference. So the power of the means to providing thermal energy is likely to be reduced and therefore the cost of these means as well.

Advantageously, said means for injecting a determined quantity of combustible mixture comprise means for regulating the flow rate of said combustible mixture, in order to regulate said first quantity of energy Q1 necessary to raise the temperature of the fluid passing through the tubular body. In addition, in a particular embodiment, the aqueous effluent and the combustible fluid are simultaneously injected into the tubular body, and said means for regulating the flow rate of said combustible mixture allow the necessary quantities to be adjusted.

Preferably, said means for supplying said first quantity of thermal energy Q1 to said aqueous effluent comprise a thermoelectric generator secured to said tubular body. In this way, it is easy to control said means by a contactor or a relay as part of a process for regulating the starting assembly.

According to a particularly advantageous arrangement, the starting assembly comprises a heat exchanger for withdrawing said fraction from said third quantity of energy Q3 and applying it to said first zone of said tubular body.

Other features and advantages of the invention will emerge on reading the description given below of particular embodiments of the invention, given by way of non-limiting indication, with reference to the appended drawings in which:

- Figure 1 is a schematic view showing an installation and a starting assembly according to the invention, as well as the general thermal profile corresponding to said installation in a determined step; and, - Figure 2 is a schematic view showing the installation and the start-up assembly according to a particular mode of implementation of the invention, as well as four thermal profiles corresponding to four stages of the starting process.

Referring to Figure 1, the constituent elements of the starter assembly according to the invention will be described, then the cooperation of these elements and the general thermal profile which may result therefrom.

The installation illustrated in Figure 1 comprises a tubular body 10, having an inlet 12 and an outlet 14 between which succeed a first zone 16 and a second zone 18. At the inlet 12 of the tubular body 10 a pump 20 allows injecting an aqueous effluent flowing from the reservoir 22, at a pressure P1 corresponding at least to the critical pressure of said aqueous effluent, in the tubular body 10. In the second zone 18 of the tubular body 10 three injection means are shown 24, 26, 28 making it possible to inject an oxidizing composition into the tubular body 10 at three injection points spaced from one another, the number of injection points being, of course, not necessarily limited to three.

A heat exchanger 30 has a first end 32 capable of absorbing the dissipated thermal energy near the outlet 14 of the tubular body 10 and a second end 34 capable of transmitting at least a fraction of said dissipated thermal energy, in the first zone 16 of the tubular body 10, near the entrance 12.

The starting assembly includes thermoelectric means 36 making it possible to supply a first quantity of energy Q1 in the first zone 16 of the tubular body 10 and means 38 for injecting a combustible mixture contained in a tank 40. Preferably, the point of injection of the fuel mixture is located between the inlet 12 and the second end 34 of the heat exchanger 30 or the thermoelectric means 36.

When the installation is in normal operation, after the start-up phase, the pump 20 continuously injects the aqueous effluent containing organic bodies, at a pressure P1 greater than the critical pressure of the effluent, into the tubular body 10, so that the pressure is greater than P1 between the inlet 12 and the outlet 14 of the tubular body 10. After the injection, the injected aqueous effluent is brought to a temperature T2 according to the profile of the curve 42, in broken lines, thanks to the second end 34 of the heat exchanger 30 which transfers a fraction of the thermal energy which it receives into its first end 32. This thermal energy is produced by the oxidation of the organic bodies contained in the aqueous effluent, which react progressively after being brought to temperature T2, with the oxidizing composition which is injected by the injection means so as to oxidize all the organic bodies contained in the effluent. Thus, the temperature gradually increases in the second zone 18 of the tubular body after each injection of oxidizing composition, to go from temperature T2 to temperature T3 after the first injection, from temperature T3 to temperature T4 after the second injection and from the temperature T (n-1) to Tn after the (n-2) ^th injection. In a preferred embodiment of the invention, the injections of oxidizing composition are adjusted so that the temperature increases continuously between T2 and Tn, the aqueous effluent passing from a subcritical state to the supercritical domain.

The invention relates precisely to the start-up of the installation and one of its characteristics resides in the injection of the combustible mixture which, by reacting, provides significant preheating means. To fulfill its role, this combustible mixture must have certain specific characteristics. Indeed, for the process to be advantageous, this mixture must react at an intermediate temperature T1, the lowest possible, in any case lower than the reaction temperature T2 at which the organic bodies contained in the aqueous effluent are capable of s 'oxidize.

In addition, in a particularly advantageous manner, the combustible mixture contains a fuel and an oxidant in substoichiometric proportion relative to the fuel so that, when the combustible mixture is at the intermediate temperature T1 the whole of the oxidant reacts with part of the fuel according to a reaction oxidation producing thermal energy and that the other part remains available to be oxidized.

Of course, the combustible mixture, after a part has reacted with the oxidant, contains oxidation products, in particular carbon dioxide. In the description, the combustible mixture also denotes the combustible mixture in which the fuel has been partially or completely oxidized and the oxidation products which it contains.

According to a particular embodiment, the combustible mixture is an aqueous mixture containing, an organic compound constituting the fuel whose concentration is less than its solubility in said aqueous mixture, and an oxidant also soluble in the aqueous mixture, for example hydrogen peroxide. Said organic compound must have a significant oxidation enthalpy, for example greater in absolute value than 3 Megajouies per mole of compound so as to release a lot of thermal energy within the aqueous mixture.

In addition, the activation energy of the mixture, organic compound / oxidizer must be sufficiently low, for example less than 1 Kilo Joules per mole of said organic compound, for the reaction to start at said temperature T1. Preferably, the activation energy is substantially equal to 0.8 Kilo Joules per mole.

In a particularly advantageous manner, the combustible mixture comprises substantially 65% of water, 30% of hydrogen peroxide and 5% of glucose. Thus, the enthalpy of reaction is 3.6 kJ / mol and the activation energy of 0.807 kJ / mol.

Referring again to FIG. 1, a general description will be given of the method for starting the installation according to the invention, which precedes the normal operation which has been described above.

During this start-up step, firstly, only the fuel mixture is injected at an initial temperature Ti in the first zone 16 upstream of the preheating means 34 and 36, at a pressure P1 and the thermoelectric means 36 are used. of so as to supply a first quantity of energy Q1 to the fuel mixture which passes through the tubular body 10 with regard to the thermoelectric means 36. In this way, the fuel mixture reaches a temperature T1 along curve 44, then thanks to the oxidation reaction that the fuel undergoes at this temperature T1 and which produces an energy Q2, the mixture then reaches the temperature T2 along curve 46.

When the combustible mixture has reached the end 48 of the first zone 16 and is at temperature T2, only part of the fuel has reacted, so that the injection of a first portion of the oxidizing composition with the injection means 24 causes the oxidation of a first fraction of the other part of the fuel and the production of thermal energy. In this way the combustible mixture reaches the temperature T3 along the curve 50, then the temperature T4 along the curve 52 when a second portion of the oxidizing composition is injected which oxidizes a second fraction of the other part of the fuel and a temperature Tn following the curve 54 when injecting an n ^'th portion of the oxidizing composition that oxidizes an ^{n th} fraction of the other part of the fuel.

When the tubular body 10 reaches the temperature Tn at output 14 and the second end 34 of the heat exchanger 30 is capable of supplying the combustible mixture with an amount of energy capable of bringing it from the initial temperature Ti to the temperature of reaction T2, the thermal equilibrium of the installation is substantially reached, and the thermoelectric means 36 are stopped, the injection of the aqueous effluent containing the organic body at the inlet 12 of the tubular body 10 and stopping the injection of the fuel mixture.

After having described, in general, the method of starting the installation in accordance with the invention, we will describe, according to a particular embodiment and with reference to Figure 2, the different stages of the starting process before reaching the thermal balance of the installation. Found in FIG. 2 are the tubular member 10 at the inlet 12 of which the aqueous effluent or / and the combustible mixture respectively are contained in the tanks 22 and 40 are injected. On the other hand, the heat exchanger has means for regulation 60 intended to modulate the fraction of thermal energy to be applied in the first zone 16 of the tubular body 10, near the entry 12. In addition, only three means of injection, 24, 26, 28 of the oxidizing composition are provided.

The four main stages of the starting process according to this embodiment will be described with reference to the four thermal profiles, P1, P2, P3, P4 situated directly above the tubular member 10.

When the installation is at rest, the tubular body 10 and the heat exchanger 30 are at ambient temperature, the aqueous effluent and the combustible mixture being at the initial temperature Ti, which is substantially equal to ambient temperature. In the first, transient step, of the start-up process according to the invention, only the combustible mixture is injected at the inlet 12 of the tubular body 10, at a pressure at least equal to P1 and the thermoelectric means are used to so as to supply the quantity of energy Q1 to the fluid which passes through the first zone 16. The means for injecting the oxidizing composition are not activated. Thus, by referring to the profile P1, the energy Q1 supplied by the thermoelectric means 36 makes it possible to bring the temperature of the combustible mixture, initially to the temperature Ti, to the temperature T1 according to the portion of curve 62. Next, the oxidation of a first part of the fuel caused by the thermal energy Q1, produces a second quantity of energy Q2, which brings the temperature of the combustible mixture to the temperature T2 according to the portion of curve 63. The thermal profile is substantially constant in the second zone of the tubular body, in this first phase, since all of the oxidant has been consumed and the oxidizing composition has not been injected.

During the second step following the first, the thermal profile of the installation corresponding to P2, only the first two means injection 24, 26 of the oxidizing composition are used. In this way, the second part of the fuel which is not oxidized in the first zone 16, for lack of oxidizer, is partially oxidized by two portions of oxidizing composition, corresponding to the implementation of the injection means 24 and 26 , so that the thermal energy produced by the oxidation increases the temperature of the combustible mixture, first by bringing it to the temperature T3 according to the portion of curve 64, then to the temperature T4 according to the portion of curve 65. The temperature remains constant at the end of the second zone 18 of the reactor.

During the transition between the first step and the second step, the thermal profiles of the first zone 16 of the tubular body 10 are substantially identical, while in the third step, the thermal profile P3 of the first zone 16 is modified. It is thanks to the thermal energy produced by the reaction of the oxidizing composition with the combustible mixture, in the second step, that the second end 34 of the heat exchanger 30 is capable of providing an amount of energy equivalent to Q1. to bring the temperature of the fuel mixture from the initial temperature Ti to the intermediate temperature T1 along the portion of curve 66. Obviously, this energy also allows the oxidation of the first part of the fuel and results in an increase in temperature of the fuel mixture at temperature T2 along the portion of curve 67. Thus, the thermoelectric means 36 are capable of being deactivated. The thermal profile of the second zone 18 of the tubular body 10 remains substantially unchanged compared to the second step.

The last step, corresponding to the thermal profile P4, constitutes the transition step between the injection of the combustible mixture and the injection of the aqueous effluent containing the organic bodies to be oxidized. During this step, the last injection means 28 of the oxidizing composition are activated, so as to oxidize the last portion of fuel contained in the combustible mixture, and thus, the energy produced increases the temperature of said mixture at temperature T5 according to the portion of curve 68. Thus, the second end 34 of the heat exchanger 30 is capable of supplying a sufficient quantity of energy to bring the fuel mixture directly, along the portion of curve 69, from the initial temperature Ti to the reaction temperature T2 at which the fuel can be oxidized by the oxidizing composition.

In this way, the installation has reached its thermal equilibrium and it is possible to switch from the injection of the combustible mixture to the injection of the aqueous effluent.

It is understood that the thermal profiles of the tubular body 10 do not change discontinuously between each phase. On the other hand, the control of the injection means or of the thermoelectric means can be carried out in an all or nothing mode. In a particularly advantageous manner, the installation start-up assembly comprises means for measuring the temperature of the tubular body 10 and control means, so as to automatically control the start-up process in accordance with the invention.

To do this, the tubular body 10 comprises a first temperature sensor between the inlet 12 and the second end of the heat exchanger 30, a second sensor between said second end 34 and the thermoelectric means 36, a third sensor between the means thermoelectric 34 and the first injection point of the oxidizing composition by the injection means 24, a fourth, a fifth and a sixth after each injection point of the oxidizing composition.

In addition, the control means comprise ^" comparison means, for comparing the temperatures measured by the sensors and control means for controlling the different injection means and the thermoelectric means. In a particular embodiment, the value of the temperature T1 measured after the preheating of the fuel mixture by the thermoelectric means 36 is between 80 and 120 ° C, by example 100 ° C and the value of the intermediate temperature T2 measured after reaction of the first part of the fuel is between 230 and 270 ° C, for example 250 ° C. According to this embodiment, the value of the temperature measured, after the first injection of the oxidizing composition, is between 280 and 320 ° C, for example 300 ° C, after the second injection, between 380 and 420 ° C, by example 400 ° C and after (a third injection, between 530 and 570 ° C, for example 550 ° C.

Thus, by assimilating the aqueous effluent to water, it is considered to reach a supercritical state after the second injection. Obviously, the invention is not limited to the embodiments described above, and in particular it has been envisaged to co-inject the aqueous effluent and the combustible mixture under certain conditions, for example, when the concentration of l The aqueous effluent in organic bodies varies during the treatment and that it is necessary to maintain the thermal balance of the installation.

In addition, an installation is provided, the tubular body of which has enlarged zones so as to increase the residence time of the reaction mixture.

Claims

1. Method for starting an installation, intended for the oxidation of organic bodies contained in an aqueous effluent, said installation comprising a tubular body (10) at the inlet (12) of which said aqueous effluent is capable of being injected at a pressure P1 corresponding at least to the critical pressure of said aqueous effluent, said tubular body (10) having a first zone (16) extending said inlet (12), a second zone (18) in which an oxidizing composition is capable of be injected, and an outlet (14), characterized in that it comprises the following stages: - a first quantity of thermal energy Q1 is provided, in said first zone (16) of said tubular body (10), capable of bringing the temperature of the fluid passing through said tubular body (10) from an initial temperature to an upper intermediate temperature T1; and,

- Is injected into said tubular body (10), at said pressure P1, between said inlet (12) and said first zone (16) of said tubular body (10), a determined quantity of a combustible mixture, capable of reacting to a temperature below the oxidation temperature of organic bodies and at least a first part of which is capable of reacting at said intermediate temperature T1 to supply a second quantity of thermal energy Q2, bringing the temperature of said fluid to a reaction temperature T2 of so that the injection of said oxidizing composition into said second zone (18) produces at least the reaction of a second part of said combustible mixture, supplying a third quantity of energy Q3 to said outlet (14) of said tubular body (10) , a fraction of said third quantity of energy Q3 being capable of being applied in said first zone (16) of said tubular body (10) to bring the temp temperature of the fluid passing through it, at least from said initial temperature to said intermediate temperature T1.

2. Method for starting an installation according to claim 1, characterized in that it ceases to provide said first amount of energy Q1 in said first zone (16) of said tubular body (10), when said fraction of said third amount of energy Q3 is at least equal to Q1.

3. Method for starting an installation according to claim 2, characterized in that the injection of said combustible mixture is stopped in order to inject said aqueous effluent at the inlet (12) of said tubular body (10) when said fraction of said third quantity of energy Q3 is at least equal to the sum of Q1 and Q2 so as to bring the temperature of the fluid which passes through said tubular body (10) from said initial temperature to said reaction temperature T2.

4. Method for starting an installation according to claim 1, characterized in that said combustible mixture comprises a fuel and an oxidant in sub-stoichiometric proportion so that a first portion of said fuel reacts with said oxidant when said combustible mixture is brought to said temperature T1 to supply said second quantity of energy Q2 and for the second portion of said fuel to react with said oxidizing composition.

5. Method for starting an installation according to claim 4, characterized in that said fuel and said oxidizer are capable of releasing an amount of energy greater than 3 Mega Joules per mole of fuel molecules.

6. Method for starting an installation according to claim 4 or 5, characterized in that said fuel has an activation energy of less than 1 Kilo Joules per mole of molecules of said fuel.

7. A method of starting an installation according to any one of claims 4 to 6, characterized in that said oxidizer consists of hydrogen peroxide.

8. Method for starting an installation according to any one of claims 1 to 5, characterized in that said fuel comprises glucose.

9. Method for starting an installation according to any one of claims 1 to 9, characterized in that said second quantity of energy Q2 that said combustible mixture is capable of supplying represents, between 40 and 80% of the sum of Q1 and Q2.

10. A method of starting an installation according to any one of claims 1 to 9, characterized in that said fuel mixture is injected at the inlet (12) of said tubular body (10).

11. Start-up assembly of an installation, intended for the oxidation of organic bodies contained in an aqueous effluent, said installation comprising a tubular body (10) at the inlet (12) of which said aqueous effluent is capable of being injected at a pressure P1 corresponding at least to the critical pressure of said aqueous effluent, said tubular body (10) having a first zone (16) extending said inlet (12), a second zone (18) in which an oxidizing composition is capable of be injected, and an outlet (14), characterized in that it comprises:

means (36, 34) for supplying, in said first zone (16) of said tubular body (10), a first quantity of thermal energy Q1, capable of bringing the temperature of the fluid which passes through said tubular body (10), from an initial temperature to an upper intermediate temperature T1; and,

- Means (40, 38) for injecting into said tubular body (10), at said pressure P1, between said inlet (12) and said first zone (16) of said tubular body (10), a determined quantity of a mixture fuel, at least a first part of which is capable of reacting at said intermediate temperature T1 to supply a second quantity of thermal energy Q2, bringing the temperature of said fluid to a reaction temperature T2 so that the injection of said oxidizing composition into said second zone (18) produces at least the reaction of a second part of said combustible mixture, supplying a third quantity of energy Q3 to said outlet (14) of said tubular body (10), a fraction of said third quantity of energy Q3 being capable of being applied in said first zone (16) of said tubular body (10) to bring the temperature of the fluid passing through it, at least from said initial temperature to said intermediate temperature Tl

12. Start-up assembly of an installation according to claim 11, characterized in that said means for injecting a determined quantity of combustible mixture comprise means for regulating the flow rate of said combustible mixture.

13. An installation start-up assembly according to claim 11 or 12, characterized in that said means for supplying said first quantity of thermal energy Q1 to said aqueous effluent comprise a thermoelectric generator (36) integral with said tubular body (10).

14. Start-up assembly of an installation according to any one of claims 11 to 13, characterized in that it comprises a heat exchanger (30) for taking said fraction from said third quantity of energy Q3 and applying it in said first zone (16) of said tubular body (10).